Border police have been blamed for a teenage girl leaving France for Syria when she was on a watch list and the state has been ordered to pay her parents €15,000 damages.

The girl, aged 17 at the time, boarded a plane from Paris-Orly to Istanbul in Turkey without being challenged by border police or other authorities and the Conseil d’Etat – France’s highest administrative court – has ruled the “negligence of the police was a fault of such a nature as to become the state’s responsibility”.

She had been reported as missing in June 2013 and was on the list of people being sought but no one at Orly stopped her when she tried to board the plane five months later. This was despite the government’s instruction from the previous year ordering tougher controls to stop young people heading to the Middle East.

The Conseil d’Etat ruled there was no reason for any easing of the restrictions and that the government had not shown the teenager had tried to evade controls in a bid to avoid being stopped.

Her parents, named only as M and Mme K in the Conseil d’Etat ruling, had demanded the state be held liable for her departure.

Although France has been on a state of alert for several years it is thought that up to 450 young people have left France to reach Iraq and Syria, although only about 20 have been identified as involved with jihadist groups. Of the 11,400 on the ‘fichier S’ watch list in France, 16% of them are minors.